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The identification and natural clonal variation of important wood extractives in populus tremuloides Fernandez, Marc Phillip

Abstract

A rapid method for the detailed compositional analysis (70 compounds) of quaking aspen (Populus tremuloides Michx.) wood extractives was developed to monitor the differences in these extractives between natural aspen clones. The method involves the removal of increment cores from standing trees, soxhlet extraction of the sampled wood with acetone, and gas chromatography / mass spectrometry (GC-MS) of the resultant extractives. Additionally, preparative chromatographic techniques were developed and employed in order to elucidate the identity of various steryl esters that co-eluted with other components and did not provide characteristic mass spectra by GC-MS. Furthermore, comparisons between high-performance liquid chromatography (HPLC) and GC-MS were made on the basis of suitability for the analysis of high molecular weight and industrially problematic steryl esters. Genetic variation in aspen wood extractives that potentially impact on the utilization of this species for pulp and paper was sought using natural clone tests. Significant (95% confidence) interclonal variation in several wood extractives was found by analysis of variance in the extractives data from nine natural clones. The interclonal variation of biosynthetically related groups was similar, and thus, the total amounts of these groups showed more significant interclonal variation than the individual components. Significant clonal differences were found in the sterols / triterpenes, steryl esters / waxes and triglycerides which are all known pitch culprits in pulp and paper making. Also, extractive compounds known to exhibit toxic effects in aquatic organisms, showed significant differences between natural aspen clones. However, in some cases (ie flavonoids) these compounds formed a part of the defense system in the living tree and thus, were affected by the presence of wood decay measured in the 10mm cores. This decay affected the levels of various phenolic extractives in this study and thus, increased the intraclonal variance such that interclonal differences in these phenolics were not significant. The assessment of bound (glycoside) salicylic acid and its precursors, benzoic acid and o-coumaric acid, as a measure of decay resistance, was found to be affected by the presence of decay and thus, was not possible in mature aspen stands where decay is prevalent.

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